Interlock system



July 11, 1939. R, L, KIRK INTERLOQK SYSTEM Filed Aug. 2, 1937 2Sheets-Sheet 1 INVENTOR flak/I A. mw/r K.

[I -|ND|CATES BOLT EXTENDED-KEY OUT OF LOC I INDICATES BOLT WITHDRAWNKEY IN LOCK.

Patented July 11, 1939 UNITED STATES PATENT OFFICE INTERLOCK SYSTEMtrustee Application August 2, 1937, Serial No. 156,889

4 Claims.

This invention relates to interlock systems in which standard locks aremechanically associated with, or related to, mechanical or electricalequipment in such a manner as to require the operation or movement ofthe respective parts or pieces of the equipment in a predeterminedsequence to predetermined positions, consecutively, before permittingoperation of or access to a major piece of apparatus controlled by, orassociated with, the equipment.

In electrical systems, for example, it has been customary to interlockthe disconnect switches, associated with a circuit breaker, in such amanner as to require the circuit to be opened at the circuit breakerbefore access could be had to the switches or their operation effected.After the circuit was so opened, the breaker was locked open and theassociated disconnect switches subsequently locked open, in sequence.The breaker was then unlocked to permit testing or repair of the circuitbreaker, with the assurance that the breaker could not be energized fromthe associated circuit while the operators were working upon the circuitbreaker.

Such interlock systems involved the employment of a lock with eachmovable part that was to be moved to a safety position, and the lockswere so related and co-ordinated that each piece of equipment in theinterlocking sequence had to be locked in its safety position before akey would be released from the associated lock to operate a succeedinglock in the prearranged sequence.

General interlocking systems of such type, and

lock structures particularly suitable for such applications, aredisclosed in my co-pending applications Serial No. 572,998 filed Nov. 4,1931 now matured into Patent No. 2,065,859, dated Dec. 29, 1936, andSerial No. 692,457 filed Oct. 6, 1933.

When a circuit breaker alone must be tested or repaired, it is isolatedby locking open the associated disconnect switches. Where, however, theabnormal condition that requires testing of the electric circuit isexternal of the breaker itself, as for example, where a section of powercable has become faulty and has had to be replaced, isolation of thebreaker is not desired since it must be utilized for phasing purposes tocheck the proper re-connection of the conductors of the repaired cablesections.

However, in view of the prescribed normal sequence of operations imposedupon the circuit breaker and the disconnect switches by the usualinterlock system for complete isolation of the breaker, additional orauxiliary locking equipment must be supplied to provide a necessaryinterlock key to permit the closing of the circuit breaker before theclosing of both disconnect switches.

An object of this invention is to provide, in an interlock system of thetype in which the keys for 5 unlocking the several devices are releasedupon the successive actuation of the devices in predetermined order, amaster lock for controlling the actuation of one of the devices, themaster lock being operable by the key which is released upon thecompletion of the sequential actuation of all other devices or,alternatively, by a key which is released by the actuation of apredetermined intermediate device in the sequence. An object is toprovide an interlock system for use with a plu- 1'5 rality of relatedelectrical devices, the system including for one electrical device amaster lock operable by the keys which are released by the interlockelements of at least two of the other electrical devices, whereby theelectrical device having the master lock may be actuated in apredetermined manner under different conditions of adjustment of theseveral associated electrical devices. A further object is to provide aninterlock system capable of enforcing the sequential operation of someor all-of several related devices, the system being of simple design andincluding no elements additional to those required for obtaining thesequential operation of all of the related devices As applied to acircuit breaker system, the invention provides a simple and inexpensiveinterlock which may be actuated to obtain the complete isolation of thecircuit breaker by locking open both disconnecting switches when work isto be done upon the circuit breaker itself. At the same time the systemwill be flexible to permit reclosing of the circuit breaker afterlooking open only one disconnecting switch, to permit test operations tobe made upon the circuit and through the circuit breaker for checkingproper phase con nections across the open disconnect switches.

By way of example, I have illustrated the application of my principle toa part of an electrical system, and the manner in which a standardinterlocking system may be modified to embody the principle of myinvention is schematically illustrated in the accompanying drawings, inwhich Figure 1 is a diagrammatic and schematic view illustrating aportion of an electrical circuit including a circuit breaker and theassociated disconnect switches, together with the associated locks ofthe interlocking system, with all parts 01 the circuit in normal closedoperating positions;

Figure 2 is a similar view with the breaker and the disconnect switcheslocked in open position and illustrates the corresponding positions ofassociated lockbolts;

Figure 3 illustrates a modification of the interlock arrangementaccording to present practice for the system in Fig. 1, in order toprovide an auxiliary key to operate the circuit breaker for phasing,without requiring the complete sequence of operation of the entireinterlocking system;

Figure 4 is a similar view of the circuit of Fig. 1 illustrating how theadvantages and flexibility of the interlock system of Fig. 3 may beprocured Without the addition of auxiliary equipment, but by making thelook at the circuit breaker a master lock according to my invention;

Figure 5 is a longitudinal sectional view of a lock cylinder of thetumbler type showing the usual arrangement of six tumblers;

Figure 6 is a transverse sectional View showing the relative arrangementof one of the tumblers and the rotating barrel in the cylinder;

Figure 'l is a side sectional view of a tumbler cylinder similar to thatof Fig. 5 provided with a set of tumblers similar to the correspondingtumblers of the cylinder lock in Fig. 5 in order to serve as a masterlock with the lock of Fig. 5;

Fig. 8 is a side View, with parts in section, of a lever type of lock.

Figure 9 is a front elevational View of the lock in Fig. 8 andillustrates the disposition of the levers in two planes at right anglesto each other;

Figure 9a is a fragmentary sectional view i1- lustrating the manner oflooking a key in a key barrel.

Figure 10 is a side elevational view of the rotating barrel of a locksimilar to that of Fig. 8 provided with only one group of levers havingthe same patterns as the corresponding levers in the lock of Fig. 8, inorder to serve as a master lock therewith; and

Figure 11 is a rear elevational View of the assembled lock of Fig. 8,showing the cam on the rotating. barrel.

In electrical transmission and distributing systems, a standardarrangement of switching equipment includes a circuit breaker andcontrolling disconnect switches therefor, such as shown in Fig. l, inwhich a circuit breaker I6 is connected in the circuit l l between twosets of disconnect switches l2 and iii. The circuit H may be anin-coming line supplying energy to a bus I4 or it may be a feederreceiving energy from the bus. For the sake of simplicity, the circuitis shown as a single diagram instead of being illustrated with the usualthree conductors of the circuit.

When any abnormal condition occurs on or in the breaker itself, thatnecessitates testing or adjusting or repair of the breaker, safetyprecautions require the opening of the disconnect switches i2 and I? sothat the parts of the circuit breaker it may not become energized whilethe operators are working thereon. By means of an interlock system suchas schematically illustrated in Fig. 1, the operator or repair man iscompelled to open the breaker, to lock it open, and then, in turn tolock each set of the disconnect switches open before being able tore-operate the breaker mechanism itself. The interlock system for thatpurpose is illustrated as including a lock l5 at the breaker, two locksl6 and I1, respectively, at the disconnect switch l2, and two locks l8and i9, respectively, at the disconnect switch [3.

The condition of each lock in the systems shown in Figs. 1 to 4 isindicated schematically by the small rectangles which represent the keyslots or keys of the several looks. A solid black rectangle, as shownfor lock H5 in Fig. 1, indicates that the lock bolt is withdrawn andthat the key is in the lock. An open rectangle, as shown for lock IS inFig. 1, indicates that the lock bolt is extended and that the key is outof the lock.

The lock l5 at the breaker co-operates with an interlocking element 2 I,schematically illustrated as connected to a bridging contact member ofthe circuit breaker, in such a manner that when the breaker is open, theinterlocking element 2| is moved into position underneath the lock I5 sothat the lock 55 may be operated to extend its bolt 22 to lock theinterlock member 2!, and, consequently to lock the breaker contactagainst movement that would close the circuit through the circuitbreaker.

The lock i5 is so arranged that its key can be removed only when thelock bolt 22 is in the extended position. Consequently, when the lockbolt is extended and the interlock element 2| of the breaker is lockedagainst movement by the operator, the key may be removed from lock l5and may then be used to unlock the lock I6 by withdrawing its bolt 23from a slot 24 in an interlock element 25 associated with the disconnectswitch ii. The disconnect switch [2 may then be moved to its openposition, which movement will move interlock element 25 to shift a slot26 into position underneath the bolt 2'! of the lock IT. The keys 99 ofthe respective lock units are retained against Withdrawal except whenthe locks are in the desired predetermined position of operation bymeans of a guide and positioning pin 9! carried by the keys adjacent thehead thereof, the pin 9i entering a gate 92 in the cylinder casing whenthe key is inserted into the key barrel and moving into an annularchannel 93 when. the key is rotated so that the key cannot be Withdrawnexcept when the key barrel is rotated to a position to align the pin 9|with the gate 92. This structure, illustrated in Figures 9 and 9a. ismore particularly described in connection with the lock structuresdisclosed in my copending application previously referred to.

When the lock 16 was operated to withdraw its bolt 23, the key for lockit was locked against removal since the key can be removed from its lookonly in the extended position of the bolt. The look I! being similarlyconstructed, its key may be removed only when the bolt 2'! is extended,which locks the interlock element 25 against movement, and locks thedisconnect switch 12 open. The key from look I? may then be employed tooperate lock it to unlock that look and to withdraw its bolt 28 from aslot 29 in an interlock bar iii associated with the disconnect switch[3. The key in lock it cannot be removed so long as the bolt 28 iswithdrawn. The disconnect switch may then be moved to its open positionand lock l9 operated to extend its bolt 32 into a slot 33 in theinterlocking bar 3!, locking disconnect switch It open. The key fromlock I5 is then removable and may be used to unlock the lock l5 at thecircuit breaker, as illustrated.

The circuit breaker It may theri be operated by electrically ormechanically operable mechanism without endangering the lives of theoperators, since the disconnect switches H and I2 are open and isolatethe breaker from any sources of energy.

The foregoing arrangement of interlock equipment, as illustrated inFigure 1 and in Figure 2, is suficient and satisfactory where access tothe breaker is desired only when work is to be done upon the breakeritself. In order to permit operation of the breaker for phasingpurposes, however, where external circuit connections might have beenchanged due to the repair of a faulty cable, only the disconnect'switchl2 be tween the breaker and the bus should be opened. Phasing equipmentmay then be connected across the terminals of the open disconnect switchl2 to determine whether the repaired cable has been connected to theproper phases, before the circuit is finally connected through to thebus. Obviously, the circuit breaker would protect such test operationsand would open if improper cable connections caused excessive currentsto flow in the circuit. This procedure is common practice for thephasing of incoming circuits before they are finally connected to thestation bus.

To permit reclosing of the circuit breaker after only disconnect switchl2 has been locked open, an additional or auxiliary lock or key box 40may be provided in order that a key may be made available to operate thelock at the circuit breaker without going through the entire sequenceinvolving opening and looking out both sets of disconnect switches. Theauxiliary key box 40 consists of a mechanism provided with twolock-operable devices 4| and 42, mechanically related, either byinternal mechanism or by external mechanism, as schematicallyillustrated by the interlocking element 43, to permit and require thejoint operations of both lock cylinders by the respective keys so thatonly one key can be removed at a time.

With such an arrangement, as shown in Figure 3, the key from lock [7,when removed, will serve to operate the lock cylinder 4! of theauxiliary key box 40 to withdraw its bolt 44 so that the interlockelement 43 may be moved to position the slot 45a under the bolt 46 ofthe lock 42. The bolt 46 of lock 42 'may then be extended into the slot45a, and the key removed from the lock 42 to be utilized to unlock thelock 15 at the circuit breaker to permit the breaker to be operated forphasing purposes. Disconnect switch l3 cannot now be unlocked.

In order to provide the same flexibility as is available with theinterlock system of Figure 3, while obviating the necessity of, and theexpense of, the auxiliary key box 40, my present invention contemplatesmaking the lock l5 at the circuit breaker a master lock. Such masterlook may be operated not only by the key which it normally contains andwhich is available to operate lock I6 at the disconnect switch I2, butthe master lock is also made to be operable by the key from the lock II.

This application is shown in Figure 4. When disconnect switch I2 islocked open, the key from lock I? may be removed to unlock lock ill atswitch I3, or it may be returned to unlock the breaker to permit thebreaker to be closed to put potential across the terminals of switch I2for phasing purposes as described above. In the latter case the normalsequence cannot be carried further since the key of lock IT is now heldat the breaker and cannot be used to unlock the lock [8 at disconnectswitch IS.

A master lock so arranged and provided in an interlocking sequence canthus be made operable by more than one key, and operable independentlyof the normal prescribed sequence of interlocking operations, andpermits a greater flexibility or control of the system at diminishedcost, without in any way sacrificing the safety features for which thebasic interlocking system is originally provided.

Any lock of standard type may be employed for the interlocldng systems,where the lock is provided with a rotatable barrel, or its equivalent,in which a group of elements are arranged to set up a combinationoperable by a particularly shaped key. Each lock for controlling any ofthe intermediate operations is arranged to be operable by only one key.The master lock which controls the operations of an element in thesequence whose operation may be desirable under different conditions canbe arranged to be operable by more than one key, according to thespecific sequence of operations desired under various conditions.

In order to provide for the master-lock feature in the interlockingsystem, any lock of the system may be made a master-lock to co-operatewith other locks of the same type in the system, by providing propercombinations of the key controlled elements, such as tumblers, levers,or the like.

In Figures 5, 6 and 7, I have illustrated a lock of the tumbler type inwhich rotation of a keyreceiving barrel 5:? in the barrel cylinder 5| iscontrolled by a plurality of spring biassed tumblers, 52, 53, 5d, 55, 56and 51. The tumblers 52 to 51, inclusive, may be made of various lengthsand a large number of combinations may be established, which require akey 58 having proper contour to raise the tumblers out of the slots 59in the rotating barrel to permit the barrel to be rotated by the key 58.As illustrated, the tumblers consists of two co-axial portions of suchsize as to be moved by the key to a position where the upper tumblerportion is in the outer cyiinder and the lower tumbler portion in thebarrel. the barrel may be rotated. The rotating barrel 59 can thenoperate an external cam 60 to move the locking bolt in a predetermineddirection.

When a lock of the foregoing type is to be employed as a master-lock, alesser number of tumblers will be used. The patterns of the tumblers ofthe master-lock will correspond to the patterns of a similar number ofcorresponding tumblers of the standard lock or looks whose key or keysare to operate the master-lock. In this case, for example, themaster-lock may have from one to five tumblers, which will be of thesame pattern as the corresponding tumblers of the lock whose key is tooperate the master lock. The remaining tumblers of the individual lockwill be different so that the entire combination will be different, thuslimiting the operation of each lock to its own key.

In Figures 3 and 10, I have illustrated a similar relationship between astandard lock and a master lock of the lever type, known commercially asthe 4-way lock. The central rotating barrel 16, into which the operatingkey is inserted, is permitted to rotate, or is held against rotation,according to the positions of eight biassed pivoted levers "ll, arrangedin four sets or pairs. Each lever is pivotally supported on a pivot pin12 and is biassed by a spring 13 to a position where the front portionor toe of the lever extends outward into a slot in the outer cylinderhousing, and the heel or back portion of the lever extends inward intothe slot in the rotatable barrel. The barrel cannot be rotated In thatposition the two tumblers part,

while. any lever extends outward into the outer cylinder housing. When akey with the proper profile is inserted in the barrel, the levers areturned around their pivots i2 and withdrawn from the slots 16 in thecylinder housing l1 into the slots '65 of the barrel, and the barrel isthereupon permitted to be rotated by the key to operate an external bolt78 through a suitable crank or cam on the outer end of the barrel 10.

When a lock of this type is used, the master lock is provided with anumber of levers less than the eight levers of the individual lock, andhaving the same patterns as the corresponding levers in the standardlock unit whose key is to be able also to operate the master lock.

Thus by the provision of a lock in the sequence, with a combination oftumblers or levers less in number than those of a standard lock, andwith corresponding contours, a special interlocking sequence may beestablished and superimposed upon the basic interlock system as avariation thereof. Obviously, one or more locks of the system may bemade to serve as master locks.

Although I have illustrated the application of this master lockarrangement to an interlocking system provided for the protection andcontrol of an electrical distributing system, it is not necessarily solimited, since the electrical system is shown here merely by way ofillustration.

My invention is therefore not limited specifically to the particulararrangements illustrated, nor to the particular designs of the locks asshown, since they may be variously modified Without departing from thespirit and scope of the invention as set forth in the appended claims.

I claim as my invention:

1. A lock system, comprising a plurality of key actuated lock unitsoperable in sequence, one of said locks being a master lock having meansfor retaining a key against release except when said master lock is in apredetermined position of operation, the other lock units eachcomprising a lock member operable by a key released by the operation ofthe next prior lock in the sequence, a captive key and means forretaining said captive key against release except upon operation of itsassociated lock member for operating the lock member of a succeedingunit, said master lock being also operable by the key released by thelock preceding the master lock in the sequence and by the key releasedby another and preselected lock unit of the system, whereby thepredetermined complete or, alternatively, an incomplete predeterminedsequential operation of all other locks must precede the operation ofthe master lock.

2. An interlock system for use with an electrical circuit including acircuit breaker in series with a line disconnect switch and a busdisconnect switch, said system including a key operated lock unit forthe circuit breaker and a key operated lock unit for each disconnectswitch, the lock unit for the circuit breaker being a master lockoperative to look said circuit breaker open and having means forretaining its key against withdrawal except when said circuit breaker islocked open, said lock units of said disconnect switches each comprisinga lock element for locking said switches closed, a captive key and meansfor retaining said captive key against release except when said switchesare open, the key from said master lock being operative to actuate thelock unit of the bus disconnect switch to permit opening of the latterto release the captive key thereof, said captive key of the lock unit ofsaid bus disconnect switch being operable to actuate either said masterlock or the lock unit of said line disconnect switch and the captive keyof the lock unit for said line disconnect switch being operable toactuate said master lock.

3. A locking system comprising a master lock having means for retaininga key against release when said master lock is in a predeterminedposition of operation, said retaining means being rem-- deredinoperative upon operation of said master lock to another position, anda plurality of key actuated lock units operable in sequence with saidmaster lock, each lock unit including a captive key and a lock memberoperable by the key released from the next prior lock in the sequence,means included in each lock unit for retaining the captive key thereofexcept upon operation of the associated lock member, said master lockbeing also operable by the key released from the lock unit preceding themaster lock in the sequence and by the key released from another andpreselected lock unit of the sequence, whereby a key for actuating saidmaster lock may be obtained upon the sequential actuation of all of saidlock units in the predetermined complete sequence or alternatively uponthe actuation of said lock units in an incomplete predeterminedsequence.

4. A locking system for controlling the operation of related equipmentcomprising a master lock having means for retaining a key againstrelease when said master lock is in a predetermined position ofoperation and for releasing said key upon operation of said master lockto another position, means associated with said master lock for placingsome of said equipment in safety condition when said master lock isoperated to key releasing position; a plurality of key actuated lockunits operable in sequence with said master lock, each lock unitincluding a captive key and a lock member operable by a key releasedfrom the next prior lock in the sequence, means included in each lockunit for retaining the captive key thereof except upon operation of theassociated lock member, the lock member of the lock unit succeeding themaster lock in the sequence being operable by the key released from themaster lock upon operation of the latter to place its associatedequipment in safety condition, said master lock being also operable bythe key released from the last lock unit in the sequence or by the keyreleased from another and predetermined lock unit of the sequence,whereby said master lock must first be operated to initiate sequentialoperation of the other lock units in the system and whereby a key foractuating said master look as a terminal lock of a sequence may beobtained upon the sequential operation of all of said lock units in apredetermined complete sequence or alternatively upon the incompletepredetermined sequential operation of some of them.

RALPH L. KIRK.

